[this is the second segment of a post started here]
It is no wonder that the earliest surviving architectural plan is that of the monastery of St Gall from the 9th century [link:http://www.e-codices.unifr.ch/en/searchresult/list/one/csg/1092]. Our sense of scale comes only in the 13th century and that of perspective much later.
Diagrams, however, abounded in medieval manuscripts. By the 12th century, diagram-based learning became the dominant mode in Western education. When the Paris theologian Peter of Poitiers wanted his students to learn the Old Testament, he designed a collection of diagrams connecting the figures of the Old Testament to each other and to the narratives in which they featured. Peter’s Compendium was hugely popular in the later Middle Ages and inspired other diagram-based works, such as universal chronicles and chronicles of English kings.